CD19 and rheumatoid arthritis: To the best of our knowledge, miR-155-5p is the only miRNA previously investigated in blood-derived CD19+ B cells in RA, and was found, by qPCR, to be significantly increased in both untreated early RA patients (n=27) and long-standing RA patients treated with MTX (n=33) compared to healthy controls (n=9) (20).